Life Cycle-Resolved Observation of Radiative Properties of Mesoscale Convective Systems
Bouniol, Dominique ; Roca, Rémy ; Fiolleau, Thomas ; Raberanto, Patrick
The evolution of radiative properties [outgoing longwave radiation (OLR) and albedo at the top of the atmosphere] over a mesoscale convective system (MCS) life cycle is assessed using five years of Scanner for Radiation Budget (ScaRaB) radiometer on board the <em>Megha-Tropiques</em> satellite merged with geostationary infrared images. The MCS life cycle is documented using a tracking algorithm. A composite approach is then implemented to document the evolution of radiative properties at each life stage at the scale of the tropical belt, in continental and oceanic regions and in specific regions. Independently of the considered region, the composites share similarities with a unique maximum in albedo and a unique minimum in OLR, values of which differ depending on the environment as well as the amplitude of both parameters over the life cycle. The unique precessing orbit of the <em>Megha-Tropiques</em> satellite allows a consideration of the albedo as a function of the local time of observation showing that the magnitude of the albedo signal is mainly controlled by the solar zenithal angle. Sensitivity tests make possible the quantification of the impact of an error in radiative properties showing that even small errors lead to substantial increment on the instantaneous cloud radiative effect. All together, these elements point toward the subtle balance between life cycle, cloud radiative properties, and phasing within the diurnal cycle to build the atmospheric radiative budget in oceanic or continental regions.</p>
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